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Choices of deck structural & flooring fasteners: types of construction screws, nails, bolts to use when building a deck, railing, or exterior stair. This article explains critical safe-construction details for decks and porches, including avoiding deck or porch collapse and unsafe deck stairs and railings.
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The Right & The Wrong Fastener Nails & Screws Used for Joist Hangers, Framing Ties, Framing Connector Plates
Our photo, above left, shows three fasteners we have found used with steel joist hangers. This photo shows the heads of each of these fasteners.
Because the new wood preservatives ACQ (alkaline copper quat) and copper azole contain significantly more copper than the older CCA-treated lumber, they are estimated to be two to four times more corrosive to metals and galvanized coatings than the CCA they are replacing.
Comparing Joist Hanger Nails, Drywell Screws, Joist Hanger Tabs, & Utility "Construction" Screws - which are acceptable?
Stainless steel utility screws: At the top of our photo (red arrow at left) is a 1 1/4" stainless steel screw used by a contractor to secure joist hangers when building the deck shown at the top of DECK & PORCH CONSTRUCTION.
The orange arrow points to a drywall screw, and the green arrow to the proper nail for steel structural fasteners, a Simpson Strong-Tie N10 DHDG 1 1/2" hot dipped galvanized "joist hanger" nail.
What about those little "Tabs" on Joist Hangers - can I just nail those in and skip the joist hanger nails?
The locating tab (red oval in our photo at left) is intended to temporarily hold the joist hanger in place (just hammer it in) while you reach down into your nail apron to grasp a handful of joist hanger nails.
The tab is not a structural fastener and cannot be relied-on for that purpose.
Notice that the Tamlyn joist hanger shown in our photo provides for two joist hanger nails that will be hammered into the sides of the sides of the joist (two from each side), and three that will be nailed into the header or rim joist or ledger board (three at each side).
Our green arrows remind us of where we should see nails in the installed joist hanger.
Key Forces that Hold Nails & Screws in Wood as Structural Connectors
Stainless steel, galvanized, as well as proprietary-coating surfaced construction screws for use with treated lumber are available and of course are fine if used as recommended. But not the two screws shown in this photo and removed from decks we inspected. In the deck we inspected and where these improper screws had been installed, the contractor agreed to remove the screws and to replace them using the proper fasteners instead.
Most treatment manufacturers recommend that fasteners and hardware in contact with the new treated wood be stainless-steel, heavily coated hot-dipped galvanized, or proprietary fasteners tested and approved by the manufacturer.
Hot-Dipped Galvanized Nails for Treated Lumber Decking
These deck construction nails, such as the joist hanger nails shown in our photo above, have three times as much zinc coating as standard G60 connectors. Examples of G185 coatings include Simpson’s Z-Max or USP Connector’s Triple-Zinc. Best Practices Guide to Residential Construction explains:
When using lumber treated with ACQ or copper azole, use hot-dipped galvanized fasteners that meet ASTM A153 with a minimum of 2 ounces of zinc coating per square foot.
Typical Nail Schedule for Metal Framing Connectors - Joist Hangers
Typical Nail Schedule for Metal Framing Connectors - Joist Hangers - Built-up Beams
Stainless Steel Nails & Screws for Decks in Salt-Exposed or Wet/Humid Climates
In very wet or humid climates, or in areas subject to salt-water spray or deicing salts, stainless steel is the best choice. Stainless steel is also recommended for tropical hardwoods, which tend to cause staining with coated nails. Both types 304 and 316 stainless steel have been tested for use with the new wood preservatives ACQ and copper azole. Type 304 is suitable for above- ground applications. Type 316 is recommended in areas subject to salt or salt water.
Watch out: Never use stainless steel in contact with galvanized steel, as the galvanized coating will quickly corrode. Where fasteners such as nails, bolts, or lags are in contact with metal connectors, use the same metal for both components.
Proprietary Deck Screw or Nail Coatings
Originally developed for use with CCA-treated lumber, many have now been tested and approved for use with ACQ and copper azole.
Our photo, left, shows two proprietary-coating coated structural screws used for decks; the right-hand most screw is hot-dip galvanized. This photo shows these 2 1/2" screws from the side view.
Grip-Rite Fas'ners® produces "PrimeGuard Ten" exterior screws that use a coating approved for exterior use with all types of treated lumber.
Prudential produces galvanized exterior deck screws such as the one shown at the right in our photo, above. These screws are warranted "for as long as you own your home" and are rated for use in untreated or CCA pressure treated wood in residential structures.
If using one of these fastener types, make sure that it is recommended by the manufacturer for the specific type of decking being installed.
Aluminum Deck Nails
Watch out: Do not use aluminum fasteners, connectors, or flashings in contact with pressure-treated wood. The copper-based waterborne preservatives will cause corrosion and premature failure.
Also see Preservative-Treated Framing Lumber.
Hidden Deck Fasteners for Deck Boards
Over time, face-nailed deck fasteners may loosen, stain the wood decking, or lead to splitting and water penetration. Particularly with higher-end decking materials, such as tropical hardwoods, more customers are opting for hidden fastening systems (see Deck & Porch Products, Manufacturers).
Each system is proprietary, and some require proprietary tools supplied by the fastener manufacturer. Some suppliers of hardwood decking recommend a specific fastener for their product and may sell the fasteners along with the decking. There are two types of systems. One, such as Deckmaster® (Grabber Construction Products), uses a right-angle bracket that fastens to the tops of the joists and screws into the underside of the decking. These are easiest to install if the installer has access from below the deck.
The other type uses individual fasteners that fit between adjacent decking planks and screw down into the top of the joist. These typically attach to the edges of the decking planks with clips or prongs.
A variation on this type called Eb-Ty (Blue Heron Enterprises) fits into slots cut into the edges of adjacent deck boards with a plate jointer (see Figure 4-5 below).
The biggest concern with hidden deck fasteners is whether they are strong enough to resist the tendency of deck boards to warp or twist. For that reason, they are best used with premium decking products, which are dimensionally stable. Tropical hardwoods and composite decking are good candidates for hidden fasteners.
-- Adapted with permission from Best Practices Guide to Residential Construction.
Guide to Selecting the Proper Deck or Porch Floor Decking Fasteners
Whether using nails or screws, make sure to choose a product that is up to the task both structurally and aesthetically. In general, screws are more expensive to buy and install, but often they make for a neater job with fewer callbacks due to boards popping up. Construction adhesives specially formulated for treated wood may be used in conjunction with nails or screws.
Nails for Use with Deck Floors - Decking
If the decking is to be nailed, use either spiral-, twist-, or ring-shanked nails to resist pullout. When using pressure-treated wood, the fasteners should be either hot- dipped galvanized, meeting ASTM A153, or stainless steel Type 304 or higher
Galvanized nails sometimes cause discoloration with redwood, cedar, and tropical hardwoods, so stainless steel is a safer choice with these materials. Aluminum nails are also an option for redwood or cedar, but they should not be used with pressure-treated wood.
The bigger the head, the better the hold-down power. At a minimum, use a casing nail, preferably a common. Some manufacturers sell special decking nails with a head size in between the two. For 5/4" decking use a 10d (3-inch) nail. For thicker decking use a 16d (3 1/2") nail.
Deck Joist & Beam Sizing Tables & A Quick Rule of Thumb for Sizing Joists
Spans, sizes and spacings for deck joists and deck beams are discussed in detai
Decking Spans for deck flooring are shown in the Table 4-4 below.
[Click to enlarge any image or table]
Screws for Use with Deck Floors - Decking
In addition to Phillips-head screws, decking screws come with square-drive and star-drive heads that allow higher torque driving without stripping the head.
Also see DECK COLLAPSE Case Study (collapse of a new code-approved deck)
and DECK FLASHING LEAKS, ROT Case Study for an example of an older deck with rot and collapse due to improper construction and missing building flashing.
-- Adapted with permission from Best Practices Guide to Residential Construction.
Hidden Deck Screws
"Hidden" deck screws are structural fasteners for connecting decking that use proprietary screws or backer connectors that do not appear on the deck surface. See:
Basic building framing information is found at FRAMING SIZE & Spacing, Age, Types.
Continue reading at DECK FASTENER CHOICES or select a topic from the More Reading links shown below.
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